use bevy::pbr::OpaqueRendererMethod;
use bevy::prelude::*;
use bevy::pbr::ExtendedMaterial;
use bevy::pbr::MaterialExtension;
use bevy::pbr::MaterialMeshBundle;
use bevy::render::render_resource::*;

type MyMat = ExtendedMaterial<StandardMaterial, MatExt>;

fn main() {
	App::new()
		.add_plugins((
			DefaultPlugins.set(ImagePlugin::default_nearest()),
			MaterialPlugin::<MyMat>::default(),
		))
		.add_systems(Startup, setup)
		.add_systems(Update, rotate)
		.run();
}

fn setup(
	mut commands: Commands,
	mut meshes: ResMut<Assets<Mesh>>,
	mut materials: ResMut<Assets<MyMat>>,
) {
	commands.spawn(MaterialMeshBundle {
		mesh: meshes.add(
			Mesh::try_from(shape::Box {
				..default()
			}).unwrap(),
		),
		transform: Transform::from_xyz(0.0, 0.5, 0.0),
		material: materials.add(ExtendedMaterial {
			base: StandardMaterial {
				base_color: Color::RED,
				opaque_render_method: OpaqueRendererMethod::Auto,
				alpha_mode: AlphaMode::Mask(0.5),
				..default()
			},
			extension: MatExt { cutoff: 0.5 },
		}),
		..default()
	});

	commands.spawn(PointLightBundle { 
		point_light: PointLight {
			intensity: 10.0,
			..default()
		},
		transform: Transform::from_xyz(-1.0, 4.5, 4.0).looking_at(Vec3::ZERO, Vec3::Y),
		..default()
	});

	commands.spawn(Camera3dBundle {
		transform: Transform::from_xyz(-1.0, 1.5, 4.0).looking_at(Vec3::ZERO, Vec3::Y),
		..default()
	});
}

#[derive(Asset, AsBindGroup, Reflect, Debug, Clone)]
struct MatExt {
	#[uniform(100)]
	cutoff: f32,
}

impl MaterialExtension for MatExt {
	fn fragment_shader() -> ShaderRef {
		"examples/shaders/dissolve.wgsl".into()
	}
}

fn rotate(
	mut query: Query<&mut Transform, With<Handle<Mesh>>>,
	time: Res<Time>,
	mut materials: ResMut<Assets<MyMat>>,
) {
	query.iter_mut().for_each(|mut t| {
		t.rotate_local_y(time.delta_seconds() / 2.0);
		t.rotate_local_z(time.delta_seconds() / 2.0);
		t.rotate_local_x(time.delta_seconds() / 2.0);
	});
	materials.iter_mut().for_each(|(_id, m)| {
		m.extension.cutoff = time.elapsed_seconds().sin().abs();
	})
}